The present application claims priority upon Japanese Patent Application No. 2001-275275 filed on Sep. 11, 2001 and Japanese Patent Application No. 2002-262998 filed on Sep. 9, 2002, which are herein incorporated by reference.
1. Field of the Invention
The present invention relates to a cam-type automatic tool-exchanging apparatus of a simple structure having a shutter-driving mechanism which can certainly synchronize a tool-exchanging operation and a shutter-opening/closing operation in a short cycle time, and can ensure high-speed operation of the overall tool-exchanging operation including the opening/closing operation of the shutter.
2. Description of the Related Art
Conventionally, as an automatic tool-exchanging apparatus, often employed is a cam-type automatic tool-exchanging apparatus which can perform tool exchanging within a quite short cycle time as short as 0.5 to 1 second, and has stability and quite a high accuracy in movement in exchanging operation. Between the automatic tool-exchanging apparatus and a machining space of a machine tool that actually performs machining, at least one shutter is provided in order to prevent cutting chip, oil and so forth generated in the machining space from scattering towards the automatic tool-exchanging apparatus.
The shutter is closed for separating between the machining space and the automatic tool-exchanging apparatus during machining operation in the machining space, and is opened upon exchanging of the tool so that the tool-exchanging arm of the automatic tool-exchanging apparatus can be inserted within the machining space. For opening/closing the shutter, it becomes necessary to move the shutter for a substantial stroke. Conventionally, for driving the shutter, a cylinder-type driving device which can obtain a large stroke has been employed. Particularly, an air cylinder using air which will not contaminate the circumference is employed as a driving source. In this kind of cylinder-type shutter driving device, the starting point and the end point of the opening/closing stroke are detected by a sensor, such as a limit switch.
In this case, while the cam-type automatic tool-exchanging apparatus is driven by a motor, the shutter is driven by the air cylinder set forth above. Since the cam-type automatic tool-exchanging apparatus and the shutter are driven using different kinds of driving source, it has been quite difficult to establish synchronization between opening/closing operation of the shutter and the tool-exchanging operation of the tool-exchanging arm in a quite short cycle time. Furthermore, while the automatic tool-exchanging apparatus can perform high-speed operation, the shutter driven by the air cylinder is required checking of the opening/closing stroke with the sensor. Particularly, it is required to wait for checking the xe2x80x9copeningxe2x80x9d before initiating the tool-exchanging operation with the tool-exchanging arm. This would cause difficulty in achieving high-speed operation regarding the entire tool-exchanging operation. Furthermore, the shutter which is opened to provide enough space for permitting exchanging of the tool is required to have a size to cover the space opened, and thus, the shutter will be quite large in size. Therefore, a large receptacle space will be necessary upon opening the shutter. Also, it becomes difficult to move the shutter at high speed.
On the other hand, in order to simply the synchronization of the opening/closing operation of the shutter and the tool-exchanging operation, it may be considered to drive the shutter with a rotary drive shaft driving a cam of the automatic tool-exchanging apparatus. However, different from a cylinder performing a stroke operation, in order to create a stroke necessary for opening/closing of the shutter from a rotary motion of the rotary drive shaft, a complicate mechanism has to be installed. For example, it may be considered to insert a mechanism, such as rack and pinion type mechanism, between the rotary drive shaft and the shutter. However, even with such construction, it is required to interpose a reversible speed reducer having a substantially large gear ratio it in order to obtain the necessary stroke for opening/closing the shutter.
In all cases, the mechanism for opening/closing the shutter sharing the rotary drive shaft for driving the cam of the automatic tool-exchanging apparatus becomes quite complicate in comparison with the air cylinder system.
The present invention has been contrived in view of the above and other problems. It is an object of the present invention to provide a cam-type automatic tool-exchanging apparatus of a simple structure having a shutter-driving mechanism which can certainly establish synchronization between a tool-exchanging operation and opening/closing operation of a shutter in a short cycle time, and which can ensure high-speed operation of the overall tool-exchanging operation including the opening/closing operation of the shutter.
In order to accomplish the above and other objects, a cam-type automatic tool-exchanging apparatus according to one aspect of the present invention comprises: a housing; an input rotary shaft provided within the housing; a rotational-motion converting cam provided within the housing, the rotational-motion converting cam being rotationally driven by the input rotary shaft and outputting a rotational motion; a lifting/lowering-motion producing cam provided within the housing, the lifting/lowering-motion producing cam being rotationally driven by the input rotary shaft and outputting a lifting/lowering motion; a tool-exchanging arm provided outside of the housing and driven by the rotational motion and the lifting/lowering motion outputted from the cams for performing a tool-exchanging operation; a shutter provided outside of the housing, the shutter to be opened/closed in accordance with the tool-exchanging operation of the tool-exchanging arm; an opening/closing-motion producing cam provided within the housing, the opening/closing-motion producing cam being rotationally driven by the input rotary shaft and outputting a shutter-opening/closing pivotal motion for opening/closing the shutter; and a shutter-driving rotary shaft provided within the housing, the shutter-driving rotary shaft outputting the shutter-opening/closing pivotal motion of the opening/closing-motion producing cam from inside of the housing to the outside.
According to another aspect of the present invention, the shutter comprises a plurality of plate members; and the plurality of plate members are made to overlap each other and the shutter is made to open according to the rotational motion of the input rotary shaft.
The cam-type automatic tool-exchanging apparatus may further comprise: a pivotal arm, the pivotal arm being pivotally supported on the housing, having on one end a cam follower engaging with the opening/closing-motion producing cam, and having on the other end a sector gear; and a driven gear provided on the shutter-driving rotary shaft and meshing with the sector gear, wherein the shutter-opening/closing pivotal motion of the opening/closing-motion producing cam is transmitted to the shutter-driving rotary shaft.
A turning radius of the sector gear can be made to be greater than a turning radius of the driven gear so that a range of rotation angle of the shutter-driving rotary shaft is set to be greater than a range of pivoting angle of the pivotal arm.
The shutter may structure a slider crank mechanism by being provided slidably on at least one slide guide for guiding sliding of the shutter, and connected to the shutter-driving rotary shaft via a crank mechanism.
The crank mechanism may comprise a rotating arm provided on the shutter-driving rotary shaft, and a plurality of stroke rods having different lengths and respectively connecting the rotating arm and the plurality of plate members, the respective stroke rods being sequentially arranged on the rotating arm in order of increasing length from a tip end side of the rotating arm toward the shutter-driving rotary shaft.
The rotational-motion converting cam, the lifting/lowering-motion producing cam, and the opening/closing motion producing cam may be formed to have cam profiles for overlapping a timing of the tool-exchanging operation and a timing of the opening/closing operation, so as to make the tool-exchanging operation of the tool-exchanging arm be performed during a period of the opening/closing operation of the shutter in parallel.
The rotational-motion converting cam, the lifting/lowering-motion producing cam, and the opening/closing motion producing cam may be provided on a single cam body, the cam body being provided on the input rotary shaft.
Features and objects of the present invention other than the above will become clear by reading the description of the present specification with reference to the accompanying drawings.